Add creator field to repoIssues. Fixes octokit#193

Author: mikedeboer

api/v3.0.0/issues.js

@@ -84,6 +84,7 @@ var issues = module.exports = {
      *  - milestone (String): Optional.  Validation rule: ` ^([0-9]+|none|\*)$ `.
      *  - state (String): Optional. open, closed, or all Validation rule: ` ^(open|closed|all)$ `.
      *  - assignee (String): Optional. String User login, `none` for Issues with no assigned User. `*` for Issues with any assigned User.
+     *  - creator (String): Optional. The user that created the issue.
      *  - mentioned (String): Optional. String User login.
      *  - labels (String): Optional. String list of comma separated Label names. Example: bug,ui,@high
      *  - sort (String): Optional.  Validation rule: ` ^(created|updated|comments)$ `.

api/v3.0.0/routes.json

@@ -26,6 +26,7 @@
             "If-None-Match",
             "Cookie",
             "User-Agent",
+            "Accept",
             "X-GitHub-OTP"
         ],
         "params": {
@@ -823,9 +824,16 @@
                     "type": "String",
                     "required": false,
                     "validation": "",
-                    "invalidmsg": "String User login, `none` for Issues with no assigned User. `*` for Issues with any assigned User.",
+                    "invalidmsg": "",
                     "description": "String User login, `none` for Issues with no assigned User. `*` for Issues with any assigned User."
                 },
+                "creator": {
+                    "type": "String",
+                    "required": false,
+                    "validation": "",
+                    "invalidmsg": "",
+                    "description": "The user that created the issue."
+                },
                 "mentioned": {
                     "type": "String",
                     "required": false,